Engine cooling system for motorcycle

ABSTRACT

An engine cooling system for a motorcycle of the present invention includes an engine that includes a crankcase and a cylinder, a water pump to supply cooling water to the engine, and a radiator that dissipates heat of internally circulating cooling water by receiving a travelling wind. The water pump is an electrically operated type including a driving motor, and disposed independently of the crankcase.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of International Application No. PCT/JP2015/059687, filed on Mar. 27, 2015 and designated the U.S., which claims the benefit of priority of the prior Japanese Patent Application No. 2014-100664, filed on May 14, 2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an engine cooling system to cool an engine in a vehicle such as a motorcycle.

BACKGROUND ART

In a conventional motorcycle, a water-cooled engine uses a rotary driving shaft, a chain, and similar part for driving a lubricating oil pump to drive a water pump with a power of a crankshaft as a driving source.

Here, in examining the necessity of the water pump in this type of vehicle, two main conditions that requires water cooling of the engine are as follows.

1) Mounting a high output engine 2) Severe using state such as a sudden stop after a continuous high load operation

Thus the necessity for the water cooling of the engine is limited, that is, in a cold start, heat generation by the engine is used for warming-up the engine itself to reduce an extra heat capacity. In accordance with a case where an excessive cooling is not required such as an early warming-up or a steady operation, it is required to control an amount of cooling water to optimize the cooling. In using an oil pump drive system, under the condition where the amount of the cooling water increases in proportion to engine speed, a thermostat has a limitation in on/off control, and there is a difficulty with precise control for improvement of fuel efficiency.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Laid-open Patent Publication No. 4-203417

SUMMARY OF INVENTION Technical Problem

In the water-cooled engine of the motorcycle, above-described structural reasons determine a layout inside the engine. This is a factor that inhibits simplification of the structure, downsizing, or similar improvement in the water-cooled engine compared with the case of an air-cooled or an oil-cooled engine. An overcooling of a combustion chamber causes to decrease thermal efficiency of the engine if the overcooling is left as it is. Further, while the basic structure is identical to the air-cooled or the oil-cooled engine, in the case of the water-cooled, restrictions on the placement of the water pump cause the necessity to fabricate especially around a crankcase by models. That is, it is actually difficult to make components in common with the air-cooled engine or similar engine. This makes the development method inefficient.

In a cooling system disclosed in Patent Literature 1, a bypass water passage is coupled to a circulating water channel to bypass a main water pump, and to the bypass water passage, an electric sub water pump that operates at least in a predetermined high temperature state of the engine is interposed. In this case, the sub water pump is used merely secondarily.

The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide an engine cooling system for a motorcycle that performs proper and precise cooling water control and effectively ensures downsizing and similar improvement.

Solution to Problem

An engine cooling system for a motorcycle of the present invention includes an engine that includes a crankcase and a cylinder, a water pump to supply cooling water to the engine, and a radiator that dissipates heat of internally circulating cooling water by receiving a travelling wind. The water pump is an electrically operated type including a driving motor, and disposed independently of the crankcase.

In the engine cooling system for the motorcycle of the present invention, the water pump is disposed such that a pump shaft of the water pump is separated from a pump shaft of an oil pump in a side view of the vehicle body, and in a vehicle body width direction, the water pump is disposed such that at least apart of the water pump is lying inside outer ends of the crankcase, the cylinder, or the radiator.

In the engine cooling system for the motorcycle of the present invention, the water pump is disposed ahead of the crankcase or the cylinder and rear of a rear end portion of a front wheel, and disposed downward of the radiator, in the side view of the vehicle body.

In the engine cooling system for the motorcycle of the present invention, the crankcase includes a balancer shaft holder ahead of a shaft of an internal crankshaft, at least a part of the water pump overlaps with respect to the balancer shaft holder in the vertical direction, and the water pump is disposed ahead of the crankcase and downward of the balancer shaft holder in the side view of the vehicle body.

In the engine cooling system for the motorcycle of the present invention, the crankcase includes a balancer shaft holder ahead of a shaft of an internal crankshaft, at least a part of the water pump overlaps with respect to the balancer shaft holder in the vertical direction, and the water pump is disposed ahead of the cylinder and upward of the balancer shaft holder in the side view of the vehicle body.

In the engine cooling system for the motorcycle of the present invention, the water pump is disposed such that the longer side direction of the water pump is disposed to extend approximately parallel to an axis line of a balancer shaft in a front view of the vehicle body.

In the engine cooling system for the motorcycle of the present invention, the cylinder includes a cylinder block and a cylinder head, internally includes a coolant passage space that covers a peripheral area of a combustion chamber, and includes a cooling water inlet and a cooling water outlet to communicate with outside of the cylinder from the coolant passage space, and both the cooling water inlet and the cooling water outlet of the cylinder are disposed on an identical one side in the vehicle body width direction.

In the engine cooling system for the motorcycle of the present invention, the coolant passage space communicates with the outside of the cylinder block by the cooling water inlet and the cooling water outlet only.

In the engine cooling system for the motorcycle of the present invention, the water pump includes a cooling water discharge port and a cooling water suction port on one side and another side in the vehicle body width direction respectively in the front view of the vehicle body, and the radiator includes a cooling water intake and a cooling water supply port on one side and another side in the vehicle body width direction respectively.

In the engine cooling system for the motorcycle of the present invention, the cylinder includes a cam chain chamber on the other side in the vehicle body width direction.

In the engine cooling system for the motorcycle of the present invention, the engine includes an oil cooler in the crankcase, the oil cooler includes a cooling water inlet, a cooling water outlet, and a coolant passage to perform heat exchange with engine lubricating oil. The oil cooler is disposed in the crankcase, and includes the cooling water outlet and the coolant passage on the other side in the vehicle body width direction. The cooling water inlet side of the oil cooler is coupled to the radiator, and the cooling water outlet side is coupled to the water pump.

Advantageous Effects of Invention

According to the present invention, the water pump is an electrically operated type driven by an electric motor. The drive system of the engine cooling system is separated from an oil pump drive system, and the drive system itself is independently driven. The drive control to the water pump by an ECU ensures the more precise flow rate control of the cooling water, and this ensures the engine to be easily maintained in the optimal cooling state. Then, the cooling water is caused to be circulated at the appropriate flow rate constantly without excess or deficiency to improve the engine output, fuel consumption performance, and similar performance.

The water pump is disposed independently separated from the crankcase to make the crankcase lying the lower portion of the vehicle body compact. This ensures the large inclination angle of the vehicle to improve the operability of the vehicle. Separating the water pump from the crankcase enhances the degree of freedom of the arrangement of the water pump to optimize the cooling path.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view illustrating a state where an engine unit according to an embodiment of the present invention is mounted on a motorcycle.

FIG. 2 is a left side view illustrating the engine unit according to the embodiment of the present invention.

FIG. 3 is a front view illustrating the engine unit according to the embodiment of the present invention.

FIG. 4 is a perspective view illustrating the engine unit according to the embodiment of the present invention.

FIG. 5A is a side view illustrating a water pump according to the embodiment of the present invention.

FIG. 5B are cross-sectional views taken along the line I-I in FIG. 5A.

FIG. 6 is a left side view illustrating an engine unit according to a second embodiment of the present invention.

FIG. 7 is a front view illustrating the engine unit according to the second embodiment of the present invention.

FIG. 8 is a left side view illustrating an engine unit according to a third embodiment of the present invention.

FIG. 9 is a front view illustrating the engine unit according to the third embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes preferred embodiments of an engine cooling system for a motorcycle according to the present invention based on the drawings.

FIG. 1 is a side view illustrating a state where an engine unit 10 is mounted on a motorcycle 100 as an application example of the present invention. FIG. 2 is a rear perspective view of the engine unit 10. Firstly, a description will be given of a schematic configuration of the motorcycle 100 with reference to FIG. 1. Including FIG. 1, in the drawings used in the following description, an arrow Fr and an arrow Rr indicate forward and backward of the vehicle respectively as necessary. An arrow R and an arrow L indicate the right side and the left side of the side of the vehicle respectively.

In FIG. 1, a vehicle body frame 101 (main frame) is made of steel or aluminum alloy material. The vehicle body frame 101 includes two right and left front forks 103 turnably supported to right and left by a steering head pipe 102 in the front portion. In the following description, illustrating or similar indication of components or members are appropriately omitted as necessary. On the upper end of the front fork 103, a handlebar is fixed via a steering bracket. On the lower portion of the front fork 103, a front wheel 104 is rotatably supported, and a front fender is fixed to cover the upper portion of the front wheel 104.

The vehicle body frame 101 integrally couples to the rear portion of the steering head pipe 102 branching into two forks rearward with a pair of right and left, and is disposed to extend from the steering head pipe 102 widening backward and downward. In this example, the vehicle body frame 101 may be what is called a diamond frame or a trellis frame, or an equivalent to them made by joining steel pipes. The vehicle body frame 101 is configured such that the engine as an integrated component of the vehicle body frame 101, which will be described later, functions as a reinforcing member of the vehicle body frame 101. From near the rear portion of the vehicle body frame 101, a seat rail 105 extends backward appropriately inclining to rise backward, and supports a seat (sitting seat).

Near the rear end lower of the vehicle body frame 101, a swing arm 107 couples swingably in the vertical direction via a pivot shaft 106. The swing arm 107 rotatably supports a rear wheel 108 on the rear end. Between the vehicle body frame 101 and the swing arm 107, a rear shock absorber is mounted. The lower end side of the rear shock absorber is coupled to both the vehicle body frame 101 and the swing arm 107 via a link mechanism. To the rear wheel 108, a driven sprocket to which a chain to transmit the power of the engine is wound around fits. The rear wheel 108 is rotatably driven via the driven sprocket. Upward the rear wheel 108, a rear fender to cover the rear wheel 108 is mounted.

Next, a description will be given of the configuration of the engine unit 10 with reference to FIG. 2 to FIG. 4. FIG. 2 is a left side view of the engine unit 10, and FIG. 3 is a front view, FIG. 4 is a perspective view of the engine unit 10. The engine unit 10 includes an engine 11. This embodiment employs a water-cooled multi-cylinder four-cycle gasoline engine. In this example, the engine 11 may be a parallel two-cylinder engine in which, for example, a first cylinder (#1) and a second cylinder (#2) are disposed side by side in right and left (vehicle-width direction). To the upper of a crankcase 13 that houses a crankshaft 12 horizontaly supported to right and left, a cylinder block 14, a cylinder head 15, and a cylinder head cover 16 integrally couple with overlapping sequentially (FIG. 2). On the lowest position, an oil pan 17 is attached. The cylinder block 14 and the cylinder head 15 constitute a cylinder. A cylinder axis line of the engine 11 is disposed appropriately inclining forward. Such engine 11 is suspended to the vehicle body frame via a plurality of engine mounts to be integrally coupled and supported to the inside of the vehicle body frame 101.

The crankcase 13 includes a crank chamber that rotatably journales the crankshaft 12 and a crank web to integratedly rotate with the crankshaft 12. Between the crank webs a connecting rod is coupled via a crank pin. On the distal end (small end portion) of the connecting rod, a piston is swingably mounted via a piston pin, and reciprocates inside the cylinder block 14 in the vertical direction. This rotatably drives the crankshaft 12.

The crankcase 13 integrally includes a transmission case 18 in the rear portion (see FIG. 2 or similar drawing). The transmission case 18 internally includes a countershaft 19 at the rear of and parallel to the crankshaft 12. The crankshaft 12 is disposed such that the one end (right side) of the crankshaft 12 projects into a clutch chamber, and on the end portion, a primary drive gear is mounted. The countershaft 19 constitutes apart of a gear shifter (transmission) housed in the transmission case 18. On the end portion projecting to the clutch chamber side, a clutch device is constituted. A clutch shaft 20 of the clutch device (FIG. 1) is disposed coaxially with the countershaft 19.

The transmission case 18 integrally includes a drive shaft 21 on the rear obliquely downward of the countershaft 19, and on the countershaft 19 and the drive shaft 21, a plurality of transmission gears are disposed in a row. These transmission gears are selectively configured meshing relationship by a gear shift device. This ensures to obtain a gear ratio desired by the gear shifter. The power of the engine 11 is finally transmitted to a drive sprocket mounted on the shaft end of the drive shaft 21 from the crankshaft 12 through the transmission. The drive sprocket rotatably drives a driven sprocket, accordingly, the rear wheel 108 via a power transmission chain.

On the other hand, the crankcase 13 includes a balancer shaft 22 ahead of the crankshaft 12 in the front portion. On the balancer shaft 22, a balancer 23 is integrally attached. Disposing the balancer 23 reduces or inhibits vibration generated from the crankshaft 12. The crankcase 13 integrally includes a balancer shaft housing 24 projecting forward that internally houses and supports the balancer shaft 22 and the balancer 23. The balancer shaft 22 is coupled to the crankshaft 12 via a gear, and is rotatably driven by the crankshaft 12 as a power source.

In a valve system of the engine 11, the cylinder head 15 includes a cam shaft 25 to control the drive of an intake cam and an exhaust cam (FIG. 2). The camshaft 25 and the crankshaft 12 mount a sprocket on each shaft end, and on the sprocket, a cam chain that is configured to travel inside a cam chain chamber 26 (schematically illustrated by a one dot chain line in FIG. 2 and FIG. 3) formed on the left side part of the engine 11 is mounted. The crankshaft 12 is coupled to the cam shaft 25 via the cam chain. This ensures a valve gear to be driven synchronized with the rotation of the crankshaft 12.

The engine 11 further includes an air intake system that supplies air-fuel mixture constituted of air (intake air) and fuel supplied from an air cleaner and a fuel supply device respectively, an exhaust system that discharges exhaust gas after burning inside the cylinder from the engine 11, a cooling system that cools the engine 11 and a lubrication system that lubricates movable parts of the engine 11, and a control system (Engine Control Unit; ECU) that controls operations of these systems. The control by the control system causes a plurality of function systems to collaborate with the above-described auxiliary machines or similar machine. This ensures the entire engine unit 10 to be performed smooth operations.

More specifically, first, in the air intake system, both the #1 and #2 cylinders open an air intake opening 27 (intake port; the schematic position is illustrated by a dotted line in FIG. 2) on the rear side of the cylinder head 15, and to the air intake opening 27, a throttle body 28 is coupled. The throttle body 28 mounts a throttle valve (not illustrated) that opens and closes an intake passage or a passage, which are formed inside the throttle body 28, corresponding to an accelerator opening to control the flow rate of the air supplied from an air cleaner 29. In this example, throttle valve shafts of the #1 and #2 cylinders are disposed coaxially, and a valve driving mechanism to drive the throttle valve shafts mechanically, or electrically or electromagnetically is included.

On the other hand, each throttle body 28 includes an injector 30 for fuel injection on the downstream side of the throttle valve, and a fuel pump supplies fuel in a fuel tank with respect to these injectors 30. Each injector 30 injects the fuel to the intake passage in the throttle body 28 at a predetermined timing by the above-described control of the control system. This ensures the cylinders of the #1 and #2 cylinders to be supplied with the air-fuel mixture of a predetermined air-fuel ratio.

Next, in the exhaust system, both the #1 and #2 cylinders open an exhaust outlet 31 (exhaust port; the schematic position is simply indicated by a dotted line in FIG. 4) on the front side of the cylinder head 15, and to the exhaust outlet 31, an exhaust pipe 32 is coupled. As illustrated in FIG. 3 and FIG. 4, the exhaust pipe 32 of each cylinder once extends downward from the exhaust outlet 31, and is coupled to a collecting pipe 33 disposed on the left side lower portion of the crankcase 13. The collecting pipe 33 includes a catalyst. Further, the exhaust pipe 32 once extends backward from the collecting pipe 33 (an exhaust pipe 32A), and inverts and curves forward to be coupled to the rear end portion of a muffler 34 disposed in the front-rear direction at the approximately center of the crankcase 13 in a vehicle body width direction. The muffler 34 may be appropriately offset to the right side in the vehicle body width direction. Further, the exhaust pipe 32 once extends forward from the muffler 34 (an exhaust pipe 32B), and inverts and curves backward to be disposed to extend to the rear of the engine 11.

Further, the lubrication system that supplies movable parts of the engine unit 10 with lubricating oil to lubricate those parts is configured. The lubrication system includes the crankshaft 12, the valve gear configured in the cylinder head 15, the cam chain to couple those parts, the transmission, and similar parts. This embodiment employs an ordinary oil pump with respect to the lubrication system, and the oil pump supplies the lubrication system with the lubricating oil sucked up from the oil pan 17.

As illustrated in FIG. 1, in the lower portion of the crankcase 13 or the transmission case 18, an oil pump 35 is disposed downward of the crankshaft 12. A pump shaft 36 to drive the oil pump 35 is coupled to the crankshaft 12 via a chain, that is, the oil pump 35 is rotatably driven by the crankshaft 12 as a power source in the crankcase 13.

In the cooling system, on the peripheral area of the cylinder including the cylinder block 14, a water jacket formed to cause cooling water to circulate is configured. As illustrated in FIG. 1 to FIG. 4, a radiator 37 to cool the cooling water supplied to the engine 11 including the water jacket is mounted. The radiator 37 is a component that dissipates the heat of the internally circulating cooling water by receiving a travelling wind. In this example, as illustrated in FIG. 3, the radiator 37 is in a rectangular shape having the long sides in the vehicle body width direction in the front view, and is supported by the vehicle body frame 101 with an appropriate forward inclined attitude from near the lower end of the above-described steering head pipe 102 to near the front of the cylinder head 15. A water pump 38 to cause the cooling water to circulate in the cooling system is disposed, and the cylinder, the radiator 37, and the water pump 38 are coupled one another by a cooling water hose 39. A connection method of the cooling water hose 39 and similar matter will be described later.

The engine cooling system of the present invention is applied to the above-described cooling system, and especially, characterized by the water pump 38 of an electrically operated type including the driving motor for the water pump 38 and disposed independently of the crankcase 13. The driving motor of the water pump 38 can be controlled driving by the ECU with an on-vehicle battery of the motorcycle 100 as a driving power supply.

As illustrated in FIG. 1, the water pump 38 is disposed such that a pump shaft 40 of the water pump 38 is separated from the pump shaft 36 of the oil pump 35 in the side view of the vehicle body.

As illustrated in FIG. 3, the water pump 38 is disposed such that at least a part of the water pump 38 is lying inside the outer end of the crankcase 13, the cylinder, or the radiator 37 in the vehicle body width direction.

Here, a description will be given of a specific exemplary configuration of the water pump 38. With reference to FIG. 5A and FIG. 5B, a casing 41 internally houses a plurality of impellers 42 that rotate around the pump shaft 40, and on the one end side and the other end side of the casing 41, a suction port 43 and a discharge port 44 for the cooling water are opened respectively. To the casing 41, an electric motor 45 for driving the pump is integrally coupled to constitute a water pump unit. In this case, an output shaft 45 a of the electric motor 45 is disposed coaxially with the pump shaft 40, and the output shaft 45 a directly couples with respect to the pump shaft 40. Such coaxial disposing of both shafts ensures the water pump unit to be configured compact. The output shaft 45 a of the electric motor 45 may be coupled to the pump shaft 40 via a gear with an appropriate gear ratio.

As illustrated in FIG. 1 and FIG. 2, the water pump 38 is disposed ahead of the crankcase 13 or the cylinder (the cylinder block 14 and the cylinder head 15) and rear of the rear end portion of a front wheel 104, and disposed downward of the radiator 37, in the side view of the vehicle body.

As described above, the crankcase 13 includes the balancer shaft housing 24 as a balancer shaft holder ahead of the shaft of the internal crankshaft 12. Then, as illustrated in FIG. 2 or similar drawing, at least a part of the water pump 38 overlaps with respect to the balancer shaft housing 24 in the vertical direction, and the water pump 38 is disposed ahead of the crankcase 13 and downward of the balancer shaft housing 24 in the side view of the vehicle body.

In this case, at least apart of the water pump 38 overlaps with respect to the balancer shaft housing 24 in the vertical direction, and the water pump 38 is disposed ahead of the cylinder and downward of the balancer shaft housing 24 in the side view of the vehicle body.

As illustrated in FIG. 3, the water pump 38 is disposed such that the longer side direction of the water pump 38 (the pump shaft 40 direction) is disposed to extend approximately parallel to a shaft axis 46 (axis line) of the balancer shaft 22 in the front view of the vehicle body.

Here, the cylinder internally includes a coolant passage space (not illustrated) that covers the peripheral area of a combustion chamber as a part of the cooling system. As illustrated in FIG. 3, the cylinder includes an inlet 47 and an outlet 48 for the cooling water to communicate with outside of the cylinder from the coolant passage space. Both the inlet 47 and the outlet 48 are disposed on an identical one side in the vehicle body width direction (in this example, right side). In this example, as illustrated in FIG. 3, lying biased to the right edge on the cylinder front face, the inlet 47 is disposed on the lower side and the outlet 48 is disposed on the upper side. These inlet 47 and outlet 48 communicate with the coolant passage space via the water jacket.

As illustrated in FIG. 3 or similar drawing, the discharge port 44 for the cooling water of the water pump 38 (see FIG. 5B) is coupled to the inlet 47 of the cylinder via a cooling water hose 39A for supplying the cooling water. The outlet 48 of the cylinder is coupled to an intake 49 disposed on the upper right edge portion of the radiator 37 via a cooling water hose 39B (upper hose). A water supply port 50 disposed on the lower left edge portion of the radiator 37 is coupled to the suction port 43 for the cooling water of the water pump 38 (see FIG. 5B) via a cooling water hose 39C (lower hose). The intake 49 and the water supply port 50 of the radiator 37 are simply indicated by dotted lines in FIG. 3 or similar drawing.

In the above-described case, in the present invention, especially, the cylinder block 14 of the cylinder includes the inlet 47 and the outlet 48 for the cooling water communicating with the outside, and the internal coolant passage space communicates with the outside of the cylinder block 14 by the inlet 47 and the outlet 48 only.

As illustrated in FIG. 3, the water pump 38 includes the discharge port 44 and the suction port 43 for the cooling water on the one side and the other side (in this example, left side) in the vehicle body width direction respectively in the front view of the vehicle body. As described above, the cylinder includes both the inlet 47 and the outlet 48 for the cooling water on the one side in the vehicle body width direction (in this example, right side). Further, as described above, the radiator 37 includes the intake 49 and the water supply port 50 for the cooling water on the right side as the one side and the left side as the other side in the vehicle body width direction respectively.

Further, as described above, the cylinder includes the cam chain chamber 26 concerning to the valve system, and as simply indicated by the one dot chain line in FIG. 3, the cam chain chamber 26 is disposed on the left side as the other side in the vehicle body width direction, and arranged parallel to the cylinder axis line along the approximately vertical direction.

In the above-described case, appropriate positions around the cooling system of the engine 11, for example, the radiator 37, the water jacket, or the engine 11 itself detect the temperature of such as the lubricating oil by a temperature sensor, and then, the detection signal is delivered to the ECU. The ECU is configured such that, based on the result of the temperature detection or measurements, the engine speed, or similar factor, the ECU appropriately controls the drive of the electric motor 45 of the water pump 38, causes the cooling water in the cooling system to circulate, and further, adjusts the flow rate of the cooling water.

In the engine unit 10 including the above-described engine cooling system, starting the engine 11 gradually raises the temperature of the engine 11. Now, as already described, the condition that requires the cooling of the engine 11 is limited mainly such as a case of a high output engine and a sudden stop after a continuous high load operation, and the optimization of the cooling is required by controlling the amount of the cooling water corresponding to the timing of the cold start and the early warming-up. When the oil pump drive system is used as in conventional methods, the proper and precise cooling control is not necessarily ensured.

In the engine cooling system of the present invention, the water pump 38 is an electrically operated type driven by the electric motor 45, the drive system of the engine cooling system is separated from the oil pump drive system, and the drive system itself is independently driven. Accordingly, the drive control to the water pump 38 by the ECU ensures the more precise flow rate control of the cooling water, and this ensures the engine 11 to be easily maintained in the optimal cooling state. Then, the cooling water is caused to be circulated at the appropriate flow rate constantly without excess or deficiency to improve the engine output and the fuel consumption performance.

Conventionally, the water pump is disposed side by side with the oil pump in the lower portion of the crankcase to use the oil pump drive system. In contrast to this, in the present invention, the water pump is disposed independently separated from the crankcase 13 to make the crankcase 13 lying on the lower portion of the vehicle body compact. This ensures the large inclination angle (bank angle) of the vehicle to improve the operability of the vehicle. Separating from the crankcase 13 enhances the degree of freedom of the arrangement of the water pump 38 to optimize the cooling path.

The pump shaft 40 of the water pump 38 is disposed separated from the pump shaft 36 of the oil pump 35 such that at least a part of the pump shaft 40 is lying inside the outer end of the crankcase 13, the cylinder, or the radiator 37.

Thus disposing the water pump 38 independently of the crankcase 13 and separated from the oil pump 35 ensures the crankcase 13 to be compact especially in the vehicle body width direction, and this ensures the large inclination angle of the vehicle to improve the operability. Disposing the water pump 38 such that a part of the water pump 38 is lying inside the outer end of the crankcase 13, the cylinder, or the radiator 37 in the vehicle body width direction ensures the similar effect.

The water pump 38 is disposed ahead of the crankcase 13 or the cylinder, and rear of the rear end portion of the front wheel 104.

Thus disposing the water pump 38 ahead of the crankcase 13 causes the water pump 38 to be lying immediately below the radiator 37. This ensures the cooling water pipe, which is conventionally disposed to extend obliquely forward from the side of the crankcase toward the radiator, to be shorten by the length of the front-rear direction of the vehicle body to improve the maintainability, the productivity or similar efficiency.

A part of the water pump 38 overlaps with respect to the balancer shaft housing 24 in the vertical direction, and the water pump 38 is disposed ahead of the crankcase 13 and downward of the balancer shaft housing 24 in the side view of the vehicle body. Thus disposing the water pump 38 so as to slide under the balancer shaft housing 24 disposed projecting ahead of the crankcase 13 ensures places, which are conventionally spaces (empty space, that is substantive dead space), to be used effectively, while the water pump 38 is caused to close with respect to the radiator 37 in the front-rear direction. This obtains a significant advantage on the layout.

The water pump 38 is disposed such that the longer side direction of the water pump 38 (the pump shaft 40) is disposed to extend approximately parallel to the shaft axis 46 of the balancer shaft 22.

Thus aligning the axis line of the balancer shaft 22 and the longer side direction of the water pump 38 ensures the water pump 38 to be disposed along the main body portion of the crankcase 13 and the balancer shaft housing 24. This ensures a plurality of these components to be efficiently disposed close one another to downsize and concentrate the mass. Then, the improvement of the operability of the vehicle is realized.

Both the inlet 47 and the outlet 48 for the cooling water to communicate with the outside the cylinder from the coolant passage space that covers the peripheral area of the combustion chamber in the cylinder are disposed on the identical one side in the vehicle body width direction.

Thus biasing the inlet 47 and the outlet 48 for the cooling water to the one side in the cylinder ensures the cooling water pipe extending from the water pump 38 to the radiator 37 through the cylinder, that is the cooling water hose 39A and the cooling water hose 39B, to be aggregated on one side of the one side. This improves the maintainability and makes the appearance beautiful.

In this case, the cylinder block 14 includes the inlet 47 and the outlet 48 for the cooling water, and the coolant passage space in the cylinder communicates with the outside of the cylinder block 14 by the inlet 47 and the outlet 48 only.

Thus making the flowing in/out of the cooling water to the engine 11 the cylinder block 14 only reduces the coolant passage communicating with the crankcase 13 and the cylinder head 15. This eliminates a care to the cooling water leakage at the joint, and improves the assembling performance and the maintainability. Further, this ensures the easier fabrication of the crankcase 13 and the cylinder head 15, and improves the productivity because the inspection of the cooling water leakage can be omitted.

In this respect, further, in common except the cylinder block 14, the compatibility with a cylinder block of a conventional air-cooled engine can be included, the air-cooled engine can be easily water cooled corresponding to the request of the engine performance. In the cylinder of the engine 11, the inlet 47 and the outlet 48 for the cooling water are close one another in the vertical direction of the vehicle body, further the radiator 37 is disposed on the approximately identical height. Then, the coolant passage can be aggregated in the vertical direction, and the cooling water pipe can be shorten to improve the maintainability. Further, the cooling water pipe can be not redundant in the vertical direction, and this ensures the beautiful appearance to be maintained even if a vehicle exposing the cooling water pipe.

The water pump 38 includes the discharge port 44 and the suction port 43 for the cooling water on the one side and the other side in the vehicle body width direction respectively, and the cylinder includes both the inlet 47 and the outlet 48 for the cooling water on the one side in the vehicle body width direction. In addition, the radiator 37 includes the intake 49 and the water supply port 50 for the cooling water on the one side and the other side in the vehicle body width direction respectively.

As illustrated in FIG. 3, disposing the cooling water inlet and outlet of the main parts of the cooling system to have an approximately O-shape in the front view of the vehicle body makes the cooling water hoses 39 (the cooling water hoses 39A to 39C) not across largely in the vehicle body width direction. This ensures the efficient piping and the beautiful appearance.

The cam chain chamber 26 is disposed lying on the left side as the other side in the vehicle body width direction.

Thus disposing both the inlet 47 and the outlet 48 for the cooling water of the cylinder block 14 or the cylinder head 15 on the opposite side to the cam chain chamber 26 makes the coolant passage from the water pump 38 to the radiator 37 through the cylinder and the oil passage from the cylinder head 15 to (return) the crankcase 13 through the cylinder block 14 oppositely disposed in the vehicle body width direction. This ensures the shape structure inside the cylinder block 14 to be configured simply, and as a result, the cylinder block 14 is ensured to be compact.

Next, a description will be given of a second embodiment of the engine cooling system for the motorcycle according to the present invention. FIG. 6 is a left side view of the engine unit 10 according to the second embodiment, and FIG. 7 is a front view of the engine unit 10 according to the second embodiment. In the second the embodiment of the present invention, as illustrated in especially FIG. 6, the crankcase 13 internally includes an oil cooler 51 that performs heat exchange with engine lubricating oil used in the lubrication system, and is configured to cause the oil pump 35 to recirculate the cooled lubricating oil.

The oil cooler 51 includes an inlet 52 and an outlet 53 for the cooling water, and the oil cooler 51 internally includes a coolant passage to cause the cooling water flowing in/out from the inlet 52 and the outlet 53 to circulate. In this example, the inlet 52, the outlet 53 and the coolant passage are disposed on the left side as the other side in the vehicle body width direction, and the inlet 52 is coupled to the water supply port 50 of the radiator 37 via a cooling water hose 39D. The outlet 53 is coupled to the suction port 43 of the water pump 38 via a cooling water hose 39E.

The cooling water cooled by the radiator 37 flows in the oil cooler 51 via the cooling water hose 39D, and cools the lubricating oil in the oil pan 17 during a process to circulate the coolant passage in the oil cooler 51. The lubricating oil cooled by the heat exchange with the oil cooler 51 is recirculated by the oil pump 35, at that time, an oil filter 54 removes impurities in the lubricating oil. The cooling water circulated the coolant passage in the oil cooler 51 is sucked in the water pump 38 via the cooling water hose 39E. The oil pump 35 and the oil filter 54 are disposed approximately side by side in the vehicle body width direction, the oil pump 35 is disposed on the one side in the vehicle body width direction, and the oil filter 54 is disposed on the other side, respectively.

The cooling system with respect to the lubricating oil is also disposed oppositely to the coolant passage from the water pump 38 to the radiator 37 through the cylinder in the vehicle body width direction. This ensures the shape structure inside the cylinder block 14 to be constituted simply. Detecting the temperature of such as the lubricating oil to appropriately control the drive of the water pump 38 based on the detection result, that is, cooling the lubricating oil in a high temperature as necessary realizes the efficient lubricating oil cooling.

Next, a description will be given of a third embodiment of the engine cooling system for the motorcycle according to the present invention. FIG. 8 is a left side view of the engine unit 10 according to the third embodiment, and FIG. 9 is a front view of the engine unit 10 according to the third embodiment. In the third embodiment of the present invention, the crankcase 13 includes the balancer shaft housing 24 as the balancer shaft holder ahead of the shaft of the internal crankshaft 12. Then, especially, at least a part of the water pump 38 overlaps with respect to the balancer shaft housing 24 in the vertical direction, and the water pump 38 is disposed ahead of the cylinder (the cylinder block 14) and upward the balancer shaft housing 24 in the side view of the vehicle body. The other configurations are substantially similar to the case of the first embodiment.

According to the third embodiment of the present invention, as illustrated in FIG. 8, disposing the water pump 38 on the intermediate region between the cylinder and the radiator 37 ensures the coolant passage to be arranged in the approximately front-rear direction. This shortens the coolant passage by the length of the vertical direction to improve the maintainability, the productivity, or similar efficiency. The cooling water pipe can be not redundant in the vertical direction, and this ensures the beautiful appearance to be maintained even if a vehicle exposing the pipe.

In the above-described third embodiment of the present invention, the water pump 38 is preferred to be disposed ahead of the cylinder and rear of the radiator 37 in the side view of the vehicle body, and at least a part of the water pump 38 overlaps the radiator 37 in the front view of the vehicle body. Thus disposing the radiator 37, the water pump 38, and the cylinder on the approximately identical height ensures the coolant passage to be configured in the approximately front-rear direction. This shortens the cooling water pipe by the length of the vertical direction to improve the maintainability and the productivity.

In the first to the third embodiments of the present invention, the entire water pump 38 is preferred to be disposed lying inside the outer end of the crankcase 13, the cylinder, or the radiator 37 in the vehicle body width direction.

While the water pump 38 is preferred to be disposed such that the longer side direction extends approximately parallel to the axis line of the crankshaft 12 or the axis line of the balancer shaft 22, the water pump 38 may slightly incline.

While the present invention has been described using various embodiments above, the present invention is not limited only to these embodiments. Changes and similar modification are possible within the scope of the present invention.

In the embodiments, while an example where the constituting members, the components or similar part of the engine cooling system are disposed on the one side or the other side in the vehicle body width direction is described, those parts may be arranged in the relation where right and left are reversed to the above-described embodiment.

INDUSTRIAL APPLICABILITY

In the present invention, the water pump is an electrically operated type driven by an electric motor, the drive control to the water pump ensures the more precise flow rate control of the cooling water, and this ensures the engine to be easily maintained in the optimal cooling state. Then, the cooling water is caused to be circulated at the appropriate flow rate constantly without excess or deficiency to improve the engine output, fuel consumption performance and similar performance. 

1. An engine cooling system for a motorcycle, comprising: an engine that includes a crankcase and a cylinder; a water pump to supply cooling water to the engine; and a radiator that dissipates heat of internally circulating cooling water by receiving a travelling wind, wherein the water pump is an electrically operated type having a driving motor, and disposed independently of the crankcase.
 2. The engine cooling system for the motorcycle according to claim 1, wherein the water pump is disposed such that a pump shaft of the water pump is separated from a pump shaft of an oil pump in a side view of the vehicle body, and in a vehicle body width direction, the water pump is disposed such that at least apart of the water pump is lying inside outer ends of the crankcase, the cylinder, or the radiator.
 3. The engine cooling system for the motorcycle according to claim 1, wherein the water pump is disposed ahead of the crankcase or the cylinder and rear of a rear end portion of a front wheel, and disposed downward of the radiator in the side view of the vehicle body.
 4. The engine cooling system for the motorcycle according to claim 1, wherein the crankcase includes a balancer shaft holder ahead of a shaft of an internal crankshaft, and at least a part of the water pump overlaps with respect to the balancer shaft holder in the vertical direction, and the water pump is disposed ahead of the crankcase and downward of the balancer shaft holder in the side view of the vehicle body.
 5. The engine cooling system for the motorcycle according to claim 1, wherein the crankcase includes a balancer shaft holder ahead of a shaft of an internal crankshaft, and at least a part of the water pump overlaps with respect to the balancer shaft holder in the vertical direction, and the water pump is disposed ahead of the cylinder and upward of the balancer shaft holder in the side view of the vehicle body.
 6. The engine cooling system for the motorcycle according to claim 4, wherein the water pump is disposed such that a longer side direction of the water pump is disposed to extend approximately parallel to an axis line of a balancer shaft in the front view of the vehicle body.
 7. The engine cooling system for the motorcycle according to claim 1, wherein the cylinder includes a cylinder block and a cylinder head, internally includes a coolant passage space that covers a peripheral area of a combustion chamber, and includes a cooling water inlet and a cooling water outlet to communicate with outside of the cylinder from the coolant passage space, and both the cooling water inlet and the cooling water outlet of the cylinder are disposed on an identical one side in the vehicle body width direction.
 8. The engine cooling system for the motorcycle according to claim 7, wherein the coolant passage space communicates with the outside of the cylinder block by the cooling water inlet and the cooling water outlet only.
 9. The engine cooling system for the motorcycle according to claim 1, wherein the water pump includes a cooling water discharge port and a cooling water suction port on one side and another side in the vehicle body width direction respectively in the front view of the vehicle body, and the radiator includes a cooling water intake and a cooling water supply port on one side and another side in the vehicle body width direction respectively.
 10. The engine cooling system for the motorcycle according to claim 1, wherein the cylinder includes a cam chain chamber on the other side in the vehicle body width direction.
 11. The engine cooling system for the motorcycle according to claim 1, wherein the engine includes an oil cooler in the crankcase, the oil cooler includes a cooling water inlet, a cooling water outlet, and a coolant passage to perform heat exchange with engine lubricating oil, the oil cooler is disposed in the crankcase, and includes the cooling water outlet and the coolant passage on the other side in the vehicle body width direction, and the cooling water inlet side of the oil cooler is coupled to the radiator, and the cooling water outlet side is coupled to the water pump. 